title: Natural carbon isotope abundance of plasma metabolites and liver tissue differs between diabetic and non-diabetic Zucker diabetic fatty rats.
abstract: BACKGROUND
  'You are what you eat' is an accurate summary for humans and animals when it comes to carbon isotope abundance. In biological material, natural(13)C/(12)C ratio is subject to minute variations due to diet composition (mainly from ingestion of C3 and C4 metabolism plants) and to the discrimination between 'light' and 'heavy' isotopes during biochemical reactions (isotope effects and isotopic fractionation).
  
  
  RESULTS
  Carbon isotopic abundance was measured in ZDF (fa/+) and ZDF (fa/fa), (lean and obese-diabetic rats respectively) fed the same diet. By analysing plasma metabolites (glucose and non-esterified fatty acids), breath and liver tissue by high-precision isotope ratio mass spectrometry, we demonstrate for the first time statistically distinguishable metabolic carbon isotope abundance between ZDF (fa/+) and ZDF (fa/fa) rats based on plasma glucose, palmitic, oleic, linoleic, arachidonic acids and bulk analysis of liver tissue (P<0.005) resulting into clear isotopic fingerprints using principal component analysis. We studied the variation of isotopic abundance between both groups for each metabolite and through the metabolic pathways using the precursor/product approach. We confirmed that lipids were depleted in (13)C compared to glucose in both genotypes. We found that isotopic abundance of linoleic acid (C18: 2n-6), even though both groups had the same feed, differed significantly between both groups. The likely reason for these changes between ZDF (fa/+) and ZDF (fa/fa) are metabolic dysregulation associated with various routing and fluxes of metabolites.
  
  
  CONCLUSIONS
  This work provides evidence that measurement of natural abundance isotope ratio of both bulk tissue and individual metabolites can provide meaningful information about metabolic changes either associated to phenotype or to genetic effects; irrespective of concentration. In the future measuring the natural abundance δ(13)C of key metabolites could be used as endpoints for studying in vivo metabolism, especially with regards to metabolic dysregulation, and development and progression of metabolic diseases.
authors.affiliation: Analytical Sciences, Nestlé Research Center, Lausanne, Switzerland.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Godin
authors.forename: Alastair B
authors.initials: AB
authors.lastname: Ross
authors.forename: Marilyn
authors.initials: M
authors.lastname: Cléroux
authors.forename: Etienne
authors.initials: E
authors.lastname: Pouteau
authors.forename: Ivan
authors.initials: I
authors.lastname: Montoliu
authors.forename: Mireille
authors.initials: M
authors.lastname: Moser
authors.forename: Sunil
authors.initials: S
authors.lastname: Kochhar
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002247:Carbon Isotopes / Q000378:metabolism; D005591:Chemical Fractionation; D003921:Diabetes Mellitus, Experimental / Q000097:blood* / Q000378:metabolism*; D005227:Fatty Acids / Q000097:blood; D005838:Genotype; D008099:Liver / Q000378:metabolism*; D055442:Metabolome; D025341:Principal Component Analysis; D051381:Rats; D011924:Rats, Zucker
chemical_list: D001786:Blood Glucose; D002247:Carbon Isotopes; D005227:Fatty Acids